> ## Documentation Index
> Fetch the complete documentation index at: https://developers.deepl.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Using Style Rules

> Create style rule lists with configured rules and custom instructions, and apply them to translations with the style_id parameter.

Style rules apply a reusable set of formatting and style conventions to your translations. A **style rule list** combines two types of rules:

* **Configured rules**: predefined options for formatting conventions, like time format, number formatting, and punctuation
* **Custom instructions**: your own natural-language instructions for requirements the predefined rules don't cover

Both are applied together during translation. You can build style rule lists in the UI at [deepl.com/custom-rules](https://deepl.com/custom-rules) or manage them programmatically with the [style rules endpoints](/api-reference/style-rules/list-all-style-rules), as shown below.

<Info>
  The Style Rules API is currently available only to Pro API subscribers.
</Info>

## Create a style rule list

Send `POST /v3/style_rules` a name, the target `language` the rules apply to, and the rules themselves:

```sh Example request theme={null}
curl -X POST https://api.deepl.com/v3/style_rules \
  --header "Authorization: DeepL-Auth-Key $API_KEY" \
  --header "Content-Type: application/json" \
  --data '{
    "name": "Technical Documentation Rules",
    "language": "en",
    "configured_rules": {
      "dates_and_times": {
        "calendar_era": "use_bc_and_ad"
      },
      "punctuation": {
        "periods_in_academic_degrees": "do_not_use"
      }
    },
    "custom_instructions": [
      {
        "label": "Tone instruction",
        "prompt": "Use a friendly, diplomatic tone",
        "source_language": "en"
      }
    ]
}'
```

```json Example response theme={null}
{
  "style_id": "a74d88fb-ed2a-4943-a664-a4512398b994",
  "name": "Technical Documentation Rules",
  "creation_time": "2024-10-01T12:34:56Z",
  "updated_time": "2024-10-01T12:34:56Z",
  "language": "en",
  "version": 1,
  "configured_rules": {
    "dates_and_times": {
      "calendar_era": "use_bc_and_ad"
    },
    "punctuation": {
      "periods_in_academic_degrees": "do_not_use"
    }
  },
  "custom_instructions": [
    {
      "id": "68fdb803-c013-4e67-b62e-1aad0ab519cd",
      "label": "Tone instruction",
      "prompt": "Use a friendly, diplomatic tone",
      "source_language": "en"
    }
  ]
}
```

The `version` field increments each time the list is modified, so you can track changes to your style rules. See the [endpoint reference](/api-reference/style-rules/create-style-rule) for all available configured rule categories and options, and the [custom instructions guide](/docs/customize/custom-instructions) for how to write instructions that work well.

## Apply style rules to a translation

Pass the list's `style_id` in a [`/v2/translate`](/api-reference/translate/request-translation) or [`/v2/document`](/api-reference/document/upload-and-translate-a-document) request. The target language of the request has to match the style rule list's `language`:

```sh Example request theme={null}
curl -X POST https://api.deepl.com/v2/translate \
  --header "Authorization: DeepL-Auth-Key $API_KEY" \
  --header "Content-Type: application/json" \
  --data '{
    "text": ["Das Treffen ist um 15:00 Uhr"],
    "source_lang": "DE",
    "target_lang": "EN",
    "style_id": "a74d88fb-ed2a-4943-a664-a4512398b994"
}'
```

All `model_type` values are supported with style rules. Style rules apply to root languages, so a list with `language: "en"` works for `EN-US` and `EN-GB` targets alike; see [How to Apply Customizations to Language Variants](/docs/customize/customizations-for-variants).

## Update a style rule list

As with glossaries, the update methods have different scopes:

* [`PATCH /v3/style_rules/{style_id}`](/api-reference/style-rules/update-style-rule) updates the list's name
* [`PUT /v3/style_rules/{style_id}/configured_rules`](/api-reference/style-rules/update-configured-rules) **replaces all** configured rules; custom instructions are not affected

Custom instructions are managed individually within a list:

* [`POST /v3/style_rules/{style_id}/custom_instructions`](/api-reference/style-rules/create-custom-instruction) adds an instruction
* [`PUT .../custom_instructions/{instruction_id}`](/api-reference/style-rules/update-custom-instruction) replaces one (all fields required)
* [`DELETE .../custom_instructions/{instruction_id}`](/api-reference/style-rules/delete-custom-instruction) removes one

To list or inspect rule lists, use [`GET /v3/style_rules`](/api-reference/style-rules/list-all-style-rules) (add `detailed=true` to include each list's rules and instructions) or [`GET /v3/style_rules/{style_id}`](/api-reference/style-rules/get-style-rule). Deleting a list with [`DELETE /v3/style_rules/{style_id}`](/api-reference/style-rules/delete-style-rule) cannot be undone.

## Limits

* Style rule lists support target languages `de`, `en`, `es`, `fr`, `it`, `ja`, `ko`, and `zh`
* There is no limit on the number of configured rules per list
* A list can hold up to 200 custom instructions (this cap may be adjusted per plan tier in the future); each instruction prompt is limited to 300 characters
* If you need more than 200 custom instructions, split your rules across multiple style rule lists for different content types